N,N''-hexane-1,6-diylbis[N'-benzylurea]

Endpoint summary

Description of key information

skin irritation (OECD 431/439): not irritating (BASF, 2012)
eye irritation (OECD 437/EpiOcular): not irritating (BASF, 2012)

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Additional information

Skin irritation

In a GLP compliant in vitro EpiDerm™ test (BASF SE, 2012) according to OECD guidelines 431 and 439, the potential of N,N''-Hexane-1,6-diylbis[N'-benzylurea] to cause dermal corrosion/irritation was assessed by a single topical application of 25 μL bulk volume (about 7 mg) of the test substance to a reconstructed three dimensional human epidermis model. For the corrosion test two EpiDerm™ tissue samples were incubated with the test substance for 3 minutes and 1 hour, respectively. The irritation test was performed with three EpiDerm™ tissue samples, which were incubated with the test substance for 1 hour followed by a 42-hours post-incubation period. Tissue destruction was determined by measuring the metabolic activity of the tissue after exposure/post-incubation using a colorimetric test. The reduction of mitochondrial dehydrogenase activity, measured by reduced formazan production after incubation with a tetrazolium salt (MTT) was chosen as endpoint. The formazan production of the test substance treated epidermal tissues is compared to that of negative control tissues. The quotient of the values indicates the relative tissue viability.

The test substance is not able to reduce MTT directly. In the corrosion test, the mean viability of the test-substance treated tissues determined after an exposure period of 3 minutes was 100%, and it was 105% after an exposure period of 1 hour. In the irritation test, the mean viability of the test-substance treated tissues determined after an exposure period of 1 hour with about 42 hours post-incubation was 105%. Based on the observed results and applying the evaluation criteria it was concluded, that N,N''-Hexane-1,6-diylbis[N'-benzylurea] does not show a skin irritation potential in the EpiDerm™ skin corrosion/irritation test under the test conditions chosen.

Eye irritation

In a GLP compliant in vitro EpiOcular™ test (BASF SE, 2012), the potential of N,N''-Hexane-1,6-diylbis[N'-benzylurea] to cause ocular irritation was assessed by a single topical application of 50 μL bulk volume (about 13 mg) of the test substance to a reconstructed three dimensional human cornea model. Two EpiOcular™ tissue samples were incubated with the test substance for 90 minutes followed by a 18-hours post-incubation period. Tissue destruction was determined by measuring the metabolic activity of the tissue after exposure/post-incubation using a colorimetric test. The reduction of mitochondrial dehydrogenase activity, measured by reduced formazan production after incubation with a tetrazolium salt (MTT) was chosen as endpoint. The formazan production of the test substance treated epidermal tissues is compared to that of negative control tissues. The quotient of the values indicates the relative tissue viability. The test substance is not able to reduce MTT directly. The mean viability of the test-substance treated tissues was 104%. Based on the observed results and applying the evaluation criteria it was concluded, that N,N''-Hexane-1,6-diylbis[N'-benzylurea] does not show an eye irritation potential in the EpiOcular™ eye irritation test under the test conditions chosen.

In a GLP compliant in vitro Bovine Corneal Opacity and Permeability Test (BASF SE, 2012) according to OECD guideline 437, the potential of N,N''-Hexane-1,6-diylbis[N'-benzylurea] to cause serious damage to the eyes was assessed by a single topical application of 750 μL of a 20% test-substance preparation to the epithelial surface of isolated bovine corneas. Three corneas were treated with the test-substance preparation for an exposure period of 4 hours. Corneal opacity was measured quantitatively as the amount of light transmission through the cornea. Permeability was measured quantitatively as the amount of sodium fluorescein dye that passes across the full thickness of the cornea. Both measurements were used to calculate an In Vitro Irritancy Score of the test substance relative to the control corneas. The mean opacity value was -2.1, the mean permeability value was 0.002 and the In Vitro Irritancy Score was -2.0. The negative control values were 5.5, 0.002 and 5.5 and the positive control values were 63.4, 3.660 and 118.3, respectively. Based on the observed results and applying the evaluation criteria it was concluded, that N,N''-Hexane-1,6-diylbis[N'-benzylurea] does not cause serious eye damage in the Bovine Corneal Opacity and Permeability Test (BCOP Test) under the test conditions chosen. The test method according to the regulatory accepted protocol at the time of reporting does not allow for the evaluation of eye irritation. The result does not exclude an irritation potential of the test substance. For final assignment of a risk phrase at present, results from another study would be needed.

Justification for classification or non-classification

Based on the available data, the test substance is not classified with regard to skin and eye irritation according to Directive 67/548/EEC (DSD) and Regulation (EC) No 1272/2008 (CLP), respectively.